There is known a machining program checking method for a numerical control device, wherein movement of a tool and cutting of a workpiece are simulated or interference between the tool and the workpiece is checked, on the bases of a machining program and data relating to the mounting of the tool specified in the machining program as a tool to be used.
In the conventional machining program checking method, however, only the tool currently in use is checked for interference. Thus, in the case of a machine tool such as a turret lathe which performs a machining operation with a plurality of tools simultaneously mounted thereon, it is probable that, even when the tool currently in use is not interfering with the workpiece, other tools mounted on the turret may interfere with the workpiece or parts of the lathe.
Conventionally, whether such interference occurs or not is determined through the operator's thought experiment at the time of preparation of a program or simulation of tool paths, but the operator's determination cannot always be perfect. If combination, disposition or the like of the tools mounted is improper, interference of tools may occur, causing damage to tool noses or to the workpiece, displacement of the spindle, etc.